A device of this type is known, especially from EP-A-0 182 091.
It is known that such a front lifting device allows the simultaneous use of at least two tools with an agricultural tractor, namely a pushed tool and a pulled tool. However, the development of front lifts runs into several difficulties which should be taken into account if one wishes to make their use more widespread.
A problem arises when the front lifting device is not used.
According to EP-A-0 182 091 the forearms may be placed and held in raised position, by the lifting means, in order to reduce the frontal space requirement of the front lifting device as far as possible. However, in the event of an erroneous maneuver of the lifting means by the operator, the latter may bring about the descent of the forearms when such a descent is not desired and may be troublesome, or even dangerous.
The invention aims, especially, to provide a lifting device which makes it possible to avoid the tiresome consequences in the event of actuation of the lifting means, while the forearms are raised and must remain so.
The lifting device may also constitute a hinderance, particularly if the operator wishes to mount a front loader at the front of his tractor. In such a case, the operator may have to remove the front lifting device beforehand, then install his front loader.
This operation of removing the front lift, for the period in which it is not being used, constitutes a troublesome constraint and a brake to the expansion of front lifting devices.
In addition, some tasks must be carried out alternately and are wholly incompatible with repeated mounting - removal operations.
EP-A-0 274 853 indeed does describe a lifting device allowing compatibility with a front loader. However, the design of this lifting device limits the ground clearance and turn radius when working. The turn radius is also limited in transport because, for folding on each side of the tractor a relatively wide lift device is required, which interferes with the wheels when they are turned.